H.323 - standard for video conferencing and point to point communications.
T.120 - Real time data conferencing protocol

Call signals and controls

• H.323 - Packet-based multimedia communications systems
• H.225 - call control protocol
• H.235 - security
• H.245 - media control protocol
• Q.931 - digital subscriber signaling
• H.450.1 - Generic functional protocol for the support of supplementary services in H.323

Voice Over IP: SIP, H.323.

Audio Codecs, Compression Algorithms

• PCM audio codec 56/64 kbps
• G.722 - audio codec for 7 Khz at 48/56/64 kbps
• G.723.1 - speech codec for 5.3 and 6.3 kbps
• G.728 - speech codec for 16 kbps
• G.729 - speech codec for 8/13 kbps
• Windows Media Audio (WMA), MP3

Video codecs

• H.261, H.263, H.264 (MPEG4 Part 10)
• MPEG-2, MPEG-4
• Windows Media Video (WMV)

Software APIs, libraries

• Open H.323
• Microsoft Video for Windows, DirectShow, DirectX

Case Studies:

Video Media Server

The main goal of the project was adding functionality to the existing software complex that was meant for video streaming from web cameras in online mode. Initial functionality provided video broadcasting in mpeg4 format, audio » in gsm. It was necessary to enable an opportunity of viewing video through the flash player embedded into a web page, i.e. everything should be transmitted in flash supported format (video » h.263, audio » mp3).

Codec Development and Porting

The developed codec is a plug-in solution for Windows and Windows Mobile platforms ranging from Desktops, to notebooks to Pocket PC's/PDAs. This plug-in solution allows users to encode voice files with the Windows / Windows Mobile based Sound Recorder applications, and can decode the files using players such as Windows Media Player. SolveITLabs also performed audio Player porting from Windows to Windows mobile platforms.

Voice IP solution for Windows Mobile 6.0

The customer needed a mobile application to allow users to apply VoIP and different IM protocols and limit use of the GSM connection on the device with Windows Mobile 6.0. By default, Windows Mobile platform does not include support of these abilities. The application should allow users to call via SIP servers directly by pressing the "Call" button or launching the standard phone feature on the Windows Mobile 6 based devices (Smartphone and Pocket PC).

Video conferencing software

The client/server software is intended for business and entertainment use. Software has two units - Windows/MAC client application and Windows/Unix server multipoint control unit (MCU) application. The video streams handled by server are distributed to the clients based on the demand. Clients may communicate with each other using a video conference chat room.

TV Tuner Project

XShift TV Tuner application is the fully DirectShow compliant software for PC with the MS Windows. This application provides the playback, recording and trimming of TV video programs video (that are stored in file buffer), which is received by PC TV tuner. Simple sliding control enables video playback (for TV program) that was received before. Time to store video depends on several parameters such as: predefined buffer size, size of output video, compression quality etc.

Reverse Bitmap Filter

Reverse Bitmaps is a DirectShow filter designed for reversing frames in the MPEG-1, MPEG-2 Streams. It was designed for playing back MPEG-1, MPEG-2 files in reverse order - from back to front. It is fully compatible with Moonlight-Elecard MPEG2 Video Decoder, Video Renderer, Overlay Mixer, Video Mixing Renderer 7 and Video Mixing Renderer 9.

IP-telephony system

Sirkus System developed a software-hardware complex for making encrypted Internet calls to and from PSTN (Public Switched Telephony Network). Was used the following PC based hardware: PhoneJack and LineJack produced by QuickNet (USA).

This system is especially attractive for small/medium businesses as it requires minimal investments in hardware, most of which is standard inexpensive PC hardware. Nevertheless, the deployment of the standard ITU H323 protocol stack enables scalability needed to satisfy the demands of larger businesses.

Technologies used

C++ for Windows and Linux, OpenH323 (www.openh323.org), OpenSSL (www.openssl.org)